Document FR-2,833,705 provides a separating drum comprising a first rod fitted with microwave beam emitters, a second rod fitted with microwave beam receivers. The separator contains a petroleum effluent from a production well. A microwave source is connected to the emitters so that each emitter can emit a microwave beam. An acquisition device records the microwave beams picked up by the receivers and the microwave beam emitted by the source.
The present invention provides a method of processing the characteristics of the microwave beams picked up by the receivers in order to determine the composition of the fluid traversed by these beams.